PREFACE 
Volume 20 of the Contributions consists of 14 parts. The first is 
an account of the Mexican and Central American species of Ficus, 
by Mr. Paul C. Standley, Assistant Curator of the United States 
National Herbarium. In this study the author has had access to a 
large series of specimens, being thus enabled to distinguish the 
characters which are really constant and consequently of specific 
value. As a result it has been found necessary to reduce to synonymy 
many of the published names. Since little attention has been devoted 
to the tropical American figs during the last 50 years, the material. 
obtained by recent collectors has yielded a comparatively large 
number of new species. 
In part 2, Mr. Henry Pittier, of the Bureau of Plant Industry, 
United States Department of Agriculture, discusses the leguminous 
genus Lonchocarpus, chiefly the species found in middle America. 
The study is based on an extensive series of specimens collected by: 
the author and on the material contained in several of the larger 
American herbaria. The genus has been much neglected in recent 
years and is now found to embrace many more species than have 
hitherto been recognized. The fuller knowledge gained by a study 
of these new species and of the older species has led to material 
changes in the accepted classification. Mr. Pittier finds that the 
middle American species are in the main distinct from extralimita] 
species in their sectional grouping. For convenience, or for purposes 
of comparison, a number of South American and West Indian species 
also are described. 
In part 3, Mr. Pittier publishes further results of his studies of 
middle American plants, chiefly trees. Most of the species described 
are new. They are distributed among 10 families, the largest number 
belonging to the Fabaceae. A feature of general interest is the rede- 
scription of the cow tree or milk tree, the ‘palo de vaca”? of Hum- 
boldt, in the light of new information, with notes on its economic 
importance. 
Part 4 consists of a revision, by Edwin Blake Payson, of the colum- 
bines of North America. The work was carried on at the University 
of Wyoming under the direction of Prof. Aven Nelson and is based 
upon the material contained in several American herbaria. The 
author had the advantage also of personal familiarity with many of 
the species in the field. The singularity and beauty of the columbines 
have given them well-merited popularity as wild flowers, and several 
Vv 
